This invention relates to an image rotation apparatus which may be used in display apparatus for displaying an image stored in digital form.
Such a display apparatus can be used to provide an operator with information contained on a document previously scanned into data processing equipment to which the apparatus is connected. Normally the information is contained on the document in vertical format but occasionally a document, such as a graph or diagram, is intended to be viewed horizontally. One solution to this problem would be to scan a "horizontal" document so that it is stored electronically in the correct orientation. Most scanners are only able to receive documents in one orientation. Furthermore some documents may have the information on them oriented both vertically and horizontally.
It would be possible to provide a display apparatus in which the viewing screen could be rotated so that whatever the orientation of a document when first presented on the screen, the screen could be rotated to bring the displayed image into the correct orientation for viewing. However such an arrangement would cause the display apparatus to be unnecessarily bulky and would also introduce the possibility of unreliability due to the mechanical movements involved.
Generally, therefore, what is required is some means of rotating the image, or parts of it, electronically. Such an operation could be performed by software in the data processing equipment but this would require an unreasonable length of time and would also use "expensive" processor time.